The DMN Validator is raising a NPE and the following error message when the following element is present:

<drools:decisionServices xmlns:drools="http://www.drools.org/kie/dmn/1.1"/>

Error message:

DMNMessage

{ severity=ERROR, type=INVALID_NAME, message='Invalid name 'null': Name cannot be null or empty', sourceId='null', exception='', feelEvent=''}